Means for reproducing X-ray images



25, 1948. B. J. EDWARDS 2,442,287 MEANS FOR REPRODUCING X-RAY IMAGESFiled Nov. 15, 1944 b L: Q

Inventor Attorneys Patented May 25, 1948 MEANS FOR REPRGDUCING X-RAYIMAGES Baden John Edwards, Cambridge, England, as-

signor to Pye Limited, Cambridge, England, a

British company Application November 15, 1944, Serial No. 563,553 InGreat Britain August 13, 1943 Claims.

The present invention relates to means for re producing X-ray images.

According to the invention, a mosaic screen is employed upon which isprojected an image produced by X-rays, the mosaic then being scanned byan electron beam which gives rise to fluctuating potentials inaccordance with the X-ray image on the screen, which potentials arecollected to give a waveform which may then be used with televisionapparatus, for constituting a reproduction of the X-ray image on a'cathode ray tube or equivalent picture reproducing device.

By means of the invention X-ray images may be reproduced at a remotepoint over television apparatus. The invention also provides a means forviewing X-ray images, in which there is no danger to the operator fromthe X-rays.

For carrying the invention into efiect, a cathode ray tube may beemployed having beam forming means and a mosaic screen comprisingnumerous small conducting particles which is arranged so as to beexposed on one side to the X-rays, and scanned on the opposite side bythe electron beam. The exposure of the mosaic on one side to the X-rayscauses the elementary.

particles of the mosaic to be charged up in dependence upon themodulation applied to the X-rays by the subject being X-rayed, thusforming an electron image on the mosaic. The electron beam which scansthe opposite side of the mosaic discharges the particles, the electronsemitted therefrom being collected by a collecting electrode arrangedadjacent to the mosaic. The fluctuating potentials arising at thecollecting electrode are then amplified and may be used to modulate atelevision transmitter, a cathode ray viewing tube, or other desiredapparatus.

In an alternative arrangement, the same side of the mosaic screen may beboth exposed to the X-rays and also scanned by the electron beam.

In order that the invention may be more clearly understood, someembodiments thereof will now be described with reference to theaccompanying diagrammatic drawings in which:

Fig. 1 depicts a schematic arrangement for viewing X-ray images.

Fig. 2 depicts on an exaggerated scale one form of construction of themosaic screen, a portion of the screen being represented as highlymagnified.

Fig. 3 depicts a modified arrangement employing an alternative form ofcathode ray tube.

Fig. 4 depicts another form of mosaic screen employed in the tube of Fi3.

In the arrangement illustrated in Fig. 1, the

X-ray image of the subject] being X-rayed by means of the X-ray tube 2is projected on to one side of the mosaic screen 3 of the cathode raytube t, the opposite side of the screen 3 being scanned by an electronbeam produced and deflected in known manner. 5 represents the electrongun oi the tube 4, 6 the beam deflecting means, and l the time baseapparatus controlling the deflecting means 6. The mosaic screen 3 may,in one embodiment, be constructed as a line wire mesh coated with aninsulating layer and then having small metallic or conducting particlesinserted in the mesh. Fig. 2 illustrates such a form of mosaic screenconstituted by a fine copper wire mesh 8 which, as depicted in thehighly magnified portion of the figure, is coated with glass insulation9 so as to leave small apertures in the glass corresponding to themeshes in the wire. These apertures are then filled with a material,such as zinc sulphide, which can be easily reduced to a metal, thematerial then being reduced to the metal so as to produce a screen 3comprising discrete metallic particles i0 carried in the glassinsulation between the meshes of the wire. The tube 4 is provided with acollector electrode ll adjacent to the mosaic screen 3 on the sidethereof which is scanned by the electron beam. For example, and asshown, the collector electrode Il may be in the form of a conductingcoating of graphite deposited on the wall of the tube surrounding themosaic,

The X-rays projected through the subject I produce an image thereof onthe mosaic screen 3, as charges on the individual particles It] thereofaccording to the intensity of the X-rays impinging thereon. The electronbeam scanning the opposite side of the mosaic discharges the particles,and the emitted electrons are collected by the collector electrode as apicture waveform which, after amplification in an amplifier I2 is usedto modulate the beam of a cathode ray viewing tube l3 so as to reproducethe X-ray image visually on the screen of the tube l3. The time baseapparatus 1 also controls the beamdefiecting means [4 of the tube 13 soas to maintain the scans of the tubes A and i3 in synchromsm.

In a modification, the converter tube 4 may be constructed so that themosaic screen may be scanned from the same side as it is exposed to theX-rays. This is exemplified by Fig. 3 which shows an arrangement similarto that of Fig. 1, but in which a converter tube 40 is employed havingthe electron gun Ethereof offset, to scan the same side of the mosaicscreen 30 as is exposed to the X-rays from the X-ray tube 2. The screen30 may be formed by discrete metallic particles 3| deposited, forexample by evaporation, upon one side of a mica. plate 32 having on theother side a metal backing 33 which constitutes the collector electrodecorresponding to the electrode ll of Fig. 1. As depicted in Fig. 4, itisadvantageous to provide the mica plate '32 with a margin 34, orequivalently, a surrounding mica ring, which is free from the metallicmosaic 3|, and to coat this surround with fluorescent material, for thepurpose of facilitatingthe focussing of the electron beam upon themosaic 3|. By preliminarily focussing the beam onto the fluorescentsurround 34 it can be seen visually, from the glowing spot produced,when the beam is properly focussed.

The form of mosaic screen 3 employed in conjunction with a separatecollector electrode H, as described with reference to Fig. 1, may beincorporated in the form of tube exemplified by Fig. 3, in place of themosaic screen 30, so that the same side of the screen 3 would, in thatcase, beboth scanned and exposed to the X-rays. Also, it will be evidentthat the form of mosaic screen 3 described may beprovided with afluorescent surround or ring, analogous to the surround 34, forfocussing purposes.

The described embodiments of the invention are but illustrative, asvarious arrangements employing the invention are possible. For instance,the signal waveform collected at the collector electrode (H, Fig. l; 33,Fig. 3) may, after amplification, be used to modulate a televisiontransmitter and transmitted over a wire or-wireless link to a remotepoint where the X-ray image is reproduced visually by means ofconventional television receiving apparatus.

I claim:

1. Apparatus for producing an electric waveform of an X-ray image,comprising a mosaic screen, consisting of small discrete particles of ametal which is photo-electrically inert to visi ble light arran ed in acathode ray tube, an X-ray tube for projecting an X-ray image upon saidscreen, means to scan said screen with an electron beam, and means tocollect electrons emitted from said screen by said beam.

2. Apparatus for producing an electric waveform ofan X-ray image,comprising acathode ray tube containing a mosaic screen consisting ofsmall discrete metallic particles, an X-ray tube for projecting an X-rayimage on to the mosaic, means, for scanning said screen with an electronbeam, means for collecting the electrons emitted from said screen tosaid beam, and a fluorescent surround in the plane of said screen forenabling the electron beam to be visually focussed.

3. Apparatus for producing an electric waveform of an X-ray image,comprising a cathode ray tube containing a mosaic screen consisting of afine wire mesh coated with insulation and having small particles of ametal which is photoelectricall inert to visible light inserted'in themesh and insulated from the wire thereof by said insulation, an X-raytube for projecting an X-ray image upon said screen, means to scan saidscreen with an electron beam, and a collecting electrode separate fromthe mosaic screen but arranged adjacent thereto for collectin theelectrons emitted from said screen by said beam.

4. Apparatus for producing an electric waveform of an X-ray image,comprising a cathode ray tube containing a mosaic screen consisting 4 ofa fine wire mesh coated with insulation and having small zinc particlesinserted in the mesh and insulated from the wire thereof by saidinsulation, an X-ray tube for projecting an X-ray image upon saidscreen, means to scan said screen withan electron beam, and a collectinelectrode separate fromzthe mosaic screen but arranged adjacentthereto'for collecting'the electrons emitted from said screen by saidbeam.

5. Apparatus for producing an electric wave- .form of an X-ray' image,comprising a cathode ray tube containing a mosaic screen consisting of afine wire mesh coated with insulation and having smallparticles of ametal which is photoelectrically inert to visible light inserted in themesh and insulated from the wire thereof by said insulation, an X-raytube for projecting an X-ray image upon one side of said screen, meansto scan said screen with an electron beam from the other side thereof,and a collecting electrode separate from the mosaic screen but arrangedadjacent thereto for collecting the electrons emitted-from said screenby said beam.

6. Apparatus iorproducing anelectric waveform of an X-ray image,comprising a cathode ray tube containing amosaic screenconsisting of afine wire mesh coated with insulation and having small metallicparticles inserted in the mesh-and-insulatedfrom the wire=thereof bysaid insulation, an X-raytubeior projecting an X-ray image upon saidscreen, means to-scan-said-screen with an electron beam, a collectingelectrode separate from themosaic screen but arranged adjacent theretofor collecting the electrons emitted from said screen by said beam, anda fluorescent surround in the plane'of said screen for enabling theelectronbeam to be visually focussed.

7. Apparatus for producing an electric waveform of an X-ray image,comprising a cathode ray tube containing a mosaic screen consistin of -aplate of insulating-materialhaving conducting particles of a metal whichis photo-electrically inert to visible light deposited as a mosaic, onone side thereof and a conducting backing on the other side thereofto-constitute a collecting electrode, an X-ray tube for projecting anX-ray image on to theconducting particles, and means for scanning saidconducting particles with an electron beam.

8. A paratus for producing an electric waveform of an X-ray image,comprising a cathode ray tube containing a mosaic screen consisting of aplate of insulating material having zinc particles deposited. as amosaic on one side'thereof and a conduct-ing backing on the other sidethereof to constitute a collecting electrode, an X-ray tube forprojecting an X-ray image on to the zinc particles and means forscanning said zinc particles with an electron beam.

9. Apparatus for producing an electric waveform of an X-ray image,comprising a cathode ray tube containing a mosaic screen consisting of'aplate of insulating material having metallic particles-deposited as amosaic onone side thereof and a conducting backing on the other sidethereof to constitute a collecting electrode, an X-ray tube forprojecting an X-ray image on to the metallic particles, means forscanning said metallic particles with an electron beam, and afluorescent surround inthe plane of said screen for enabling theelectron beam to be visually i'ocussed.

10. Apparatus for producing an electric waveform of an X-ray image,comprising a cathode 5 6 ray tube containing a mosaic screen consistingNumber Name Date of small discrete particles of a metal which is2,083,995 Henroteau June 15. 1937 photo-electrically inert tovisiblelight, an X-ray 2,100,259 McGee Nov. 23, 1937 tube for projecting anX-ray image on to the 2,219,113 Ploke Oct. 22, 1940 mosaic, means forscanning said screen with an 5 2,234,806 Ploke Mar. 11, 1941 electronbeam, means for collecting the electrons 2,319,712 Williams May 18, 1943emitted from said screen to said beam, and a fluorescent surround in theplane of said screen FOREIGN, PATENTS for enabling the electron beam tobe visually Number Country Date focussed. 10 315,362 Great Britain Feb.12, 1931 BADEN JOHN EDWARDS. 511,796 Great Britain Aug. 24, 1939REFERENCES CITED THER REFERENCES The following references are of recordin the X-Rays and Electrons by p 1926, file of this patent: 15 ag 1UNITED STATES PATENTS 11 7Pract1cal Television, by Larner, 928, pageNumber Name Date Proceedings I. R. 13., May 1940.

2,021,907 Zworykin Nov. 26, 1935

